I. Field of the Invention
The present invention relates generally to torque meters and, more particularly, to a torque meter particularly suited for measuring the torque of the lay shaft for a propeller aircraft engine.
II. Description of the Prior Art
In propeller aircraft engines, the engine rotatably drives the propeller through a gearbox. Within the gearbox assembly a lay shaft is rotatably mounted to the housing by bearing assemblies and includes both a forward and rear end. In addition, the lay shaft is axially movable by a small amount with respect to the housing between a forward and a retracted position.
Typically, the engine is mechanically coupled to the lay shaft through a helical gear arrangement so that, as the positive torque on the lay shaft increases, the lay shaft is axially urged towards its forward position with a force proportional to the shaft torque. In the event of an engine malfunction, however, the propeller, in effect, attempts to rotatably drive the engine rather than vice versa. In doing so, the lay shaft torque reverses thus urging the lay shaft towards its rearward position.
It is important to rapidly detect the occurrence of a negative torque condition since the continuance of a negative torque condition can result in damage to the engine, the propeller and its associated components, as well as the aircraft. Consequently, many of the previously known aircraft engines include means for determining torque and for advising the pilot of the occurrence of the negative torque condition. Such indicators allow the pilot to take precautionary steps in the event of an engine malfunction, such as feathering the propeller.
One disadvantage of previously known systems is that the aircraft, its engine and/or propeller can become excessively damaged even within the relatively short period between the occurrence of the negative torque condition and the corrective action, if any, taken by the pilot.